Final answer:
A healthy red blood cell placed in a 0.9% saline solution will b. remain in the healthy state because the solution is isotonic, meaning the water exchange is balanced, and the cell retains its normal volume and shape.
Step-by-step explanation:
Placing a healthy red blood cell into a solution of 0.9% saline will cause the cell to remain in the healthy state. This is because a 0.9% saline solution is isotonic to the red blood cells. In an isotonic solution, the amounts of water entering and leaving the cell are equal, maintaining the cell's volume and shape. Red blood cell membranes are water permeable and will maintain their normal volume and shape in an isotonic saline solution.
In contrast, if red blood cells are placed in a hypertonic solution, they will shrivel due to water leaving the cell, a process known as crenation. On the other hand, in a hypotonic solution, red blood cells will swell and potentially burst, in a process called hemolysis, because water will rush into the cell to equalize the solute concentration. However, neither of these situations occurs with a 0.9% saline solution which is isotonic and, as such, supports the cells' structural integrity.